This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [RFC][LIBGCC][2 of 2] 64 bit divide implementation for processor without hw divide instruction
- From: Richard Earnshaw <rearnsha at arm dot com>
- To: Kugan <kugan dot vivekanandarajah at linaro dot org>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, "ian at airs dot com" <ian at airs dot com>, "patches at linaro dot org" <patches at linaro dot org>
- Date: Tue, 26 Nov 2013 15:07:28 +0000
- Subject: Re: [RFC][LIBGCC][2 of 2] 64 bit divide implementation for processor without hw divide instruction
- Authentication-results: sourceware.org; auth=none
- References: <52900902 dot 9020602 at linaro dot org> <52900AEC dot 2060301 at linaro dot org>
On 23/11/13 01:54, Kugan wrote:
> Hi All,
>
> This RFC patch enables new divide algorithm for ARMV7-A
>
> Regression tested on arm-none-linux-gnueabi with no issues.
>
> OK?
>
> Thanks,
> Kugan
>
> +2013-11-22 Kugan Vivekanandarajah <kuganv@linaro.org>
> +
> + * libgcc/config/arm/pbapi-lib.h (HAVE_NO_HW_DIVIDE): Define for
It's bpabi-lib.h
> + __ARM_ARCH_7_A__.
> +
>
>
No, this will:
1) Do the wrong thing for Cortex-a7, A12 and A15 (which all have HW
divide, and currently define __ARM_ARCH_7_A__).
2) Do the wrong thing for v7-M and v7-R devices, which have Thumb HW
division instructions.
3) Do the wrong thing for all pre-v7 devices, which don't have HW division.
I think the correct solution is to test !defined(__ARM_ARCH_EXT_IDIV__)
R.
> p2.txt
>
>
> diff --git a/libgcc/config/arm/bpabi-lib.h b/libgcc/config/arm/bpabi-lib.h
> index e0e46a6..85171c8 100644
> --- a/libgcc/config/arm/bpabi-lib.h
> +++ b/libgcc/config/arm/bpabi-lib.h
> @@ -75,3 +75,7 @@
> helper functions - not everything in libgcc - in the interests of
> maintaining backward compatibility. */
> #define LIBGCC2_FIXEDBIT_GNU_PREFIX
> +
> +#if defined(__ARM_ARCH_7A__)
> +# define HAVE_NO_HW_DIVIDE
> +#endif
>